3.4 Acoustical measurement and violin making 

 

In the last few decades there has been a significant shift in the pattern of research into violin acoustics: there are probably fewer professional scientists involved than there were, but the gap has been more than filled by a growth in activity by instrument makers.

 

The name most strongly associated with deliberate manipulation of free-plate modes in an effort to control the quality of the complete violin is that of the late American instrument maker Carleen Hutchins: in a string of publications and demonstrations spanning many years, she developed a system of free plate tuning that was influential among many makers.

 

The approach still has its adherents, but it has generally fallen out of favour since a study by German violin maker Martin Schleske in which experimental modal testing was done at many stages during the construction of a violin to chart the influence of each operation on both free plate frequencies and whole-body frequencies. Schleske’s conclusion was that the correlation between the two is not strong. The change in boundary conditions when the box is assembled is so strong that it is hard to follow the details in a way that is useful in the workshop.

One area where free-plate frequencies have a continuing interest for makers is as a way to give a simple estimate of wood properties: approximate formulae have been proposed by which long-grain and cross-grain stiffness of wood can be quantified using certain free-plate frequencies. Some authors have developed the idea of characterizing stiffness further by proposing models for whole-body behaviour that take free-plate data as input.

 

In a pioneering study, Sirr and Waddle  showed that a wealth of information can be gained, with no risk of damage to the instrument, by putting a violin through a medical CT scanner.

 

The personal computer is becoming another workshop tool, alongside the knife and the thickness calliper. Some use it as a more reliable way to find tap tones, but the language of modal analysis is spreading through the world of violin makers, and some surprisingly sophisticated studies have been carried out, especially using the software developed by Stoppani.